[clangd] Add include-fixer fixit for no_member_template diagnostic.

[kadircet]

thanks!

clang-tools-extra/clangd/IncludeFixer.cpp

std::vector<Fix> IncludeFixer::fix(DiagnosticsEngine::Level DiagLevel,
   case diag::err_no_template:
   case diag::err_no_template_suggest:
   case diag::err_undeclared_use:
   case diag::err_undeclared_use_suggest:
   case diag::err_undeclared_var_use:
   case diag::err_undeclared_var_use_suggest:
   case diag::err_no_member: // Could be no member in namespace.
   case diag::err_no_member_suggest:
+  case diag::err_no_member_template:
+  case diag::err_no_member_template_suggest:
     if (LastUnresolvedName) {
       // Try to fix unresolved name caused by missing declaration.
       // E.g.
       //   clang::SourceManager SM;
       //          ~~~~~~~~~~~~~
       //          UnresolvedName
       //   or
       //   namespace clang {  SourceManager SM; }

clang-tools-extra/clangd/unittests/DiagnosticsTests.cpp

 }
 }
 void bar() {
   ns::$qualified1[[X]] x; // ns:: is valid.
   ns::$qualified2[[X]](); // Error: no member in namespace
 
   ::$global[[Global]] glob;
 }
+using Type = ns::$template[[Foo]]<int>;
   )cpp");
   auto TU = TestTU::withCode(Test.code());
   auto Index = buildIndexWithSymbol(
       {SymbolWithHeader{"ns::X", "unittest:///x.h", "\"x.h\""},
-       SymbolWithHeader{"Global", "unittest:///global.h", "\"global.h\""}});
+       SymbolWithHeader{"Global", "unittest:///global.h", "\"global.h\""},
+       SymbolWithHeader{"ns::Foo", "unittest:///foo.h", "\"foo.h\""}});
   TU.ExternalIndex = Index.get();
 
   EXPECT_THAT(
       TU.build().getDiagnostics(),
       UnorderedElementsAre(
           AllOf(Diag(Test.range("unqualified1"), "unknown type name 'X'"),
                 DiagName("unknown_typename"),
                 WithFix(Fix(Test.range("insert"), "#include \"x.h\"\n",
                             "Add include \"x.h\" for symbol ns::X"))),
           Diag(Test.range("unqualified2"), "use of undeclared identifier 'X'"),
           AllOf(Diag(Test.range("qualified1"),
                      "no type named 'X' in namespace 'ns'"),
                 DiagName("typename_nested_not_found"),
                 WithFix(Fix(Test.range("insert"), "#include \"x.h\"\n",
                             "Add include \"x.h\" for symbol ns::X"))),
           AllOf(Diag(Test.range("qualified2"),
                      "no member named 'X' in namespace 'ns'"),
                 DiagName("no_member"),
                 WithFix(Fix(Test.range("insert"), "#include \"x.h\"\n",
                             "Add include \"x.h\" for symbol ns::X"))),
           AllOf(Diag(Test.range("global"),
                      "no type named 'Global' in the global namespace"),
                 DiagName("typename_nested_not_found"),
                 WithFix(Fix(Test.range("insert"), "#include \"global.h\"\n",
-                            "Add include \"global.h\" for symbol Global")))));
+                            "Add include \"global.h\" for symbol Global"))),
+          AllOf(Diag(Test.range("template"),
+                     "no template named 'Foo' in namespace 'ns'"),
+                DiagName("no_member_template"),
+                WithFix(Fix(Test.range("insert"), "#include \"foo.h\"\n",
+                            "Add include \"foo.h\" for symbol ns::Foo")))));
 }
 
 TEST(IncludeFixerTest, MultipleMatchedSymbols) {
   Annotations Test(R"cpp(// error-ok
 $insert[[]]namespace na {
 namespace nb {
 void foo() {
   $unqualified[[X]] x;